Das Projekt "Implications of the biogenic character on aquatic food chain accumulation of elemental selenium" wird/wurde gefördert durch: Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung. Es wird/wurde ausgeführt durch: Fachhochschule beider Basel - Nordwestschweiz.Selenium is a double edged chemical element, since it is both essential yet highly toxic. Besides its high acute toxicity, selenium is characterized to be strongly bioconcentrated from dissolved selenium species (selenite, selenate, selenoaminoacids) in aquatic primary producers and further biomagnified during food chain transfer. In consequence, water borne selenium concentrations of as little as 2 myg / L have been documented to cause severely adverse effects on top predators such as water birds and fish. Although the ecotoxic impact was first noticed in the early 1980s, to date no definitive solution has been found to remediate selenium contaminated drainage and waste waters. Due to the water insolubility of elemental selenium, the dogma that 'elemental selenium is not bioavailable and not toxic' dominates current scientific literature and forms the basis for various remediation approaches using microorganisms to convert selenium oxyanions to elemental selenium. However, a number of considerations and recent studies suggest that the dogma might only be true for 'bulk' elemental selenium, yet not for microbially formed, so called biogenic selenium. Biogenic differs from bulk elemental selenium considerably regarding its physico-chemical properties. Biogenic elemental selenium consists of nanometer sized spheres, which do not crystallize to larger particles of trigonal elemental selenium, the thermodynamically stable allotrope. The latter is due to stabilization by proteins associated with the particles. As a consequence, biogenic elemental selenium does not settle yet remains in waters as a colloidal suspension, thus being subject to uptake by biota. Although the general bioavailability of biogenic elemental selenium has been proven, it has not been studied in detail, in particular not in aquatic environments. We aim at quantifying acute and chronic toxicity in the model organism Daphnia magna, elucidating the underlying mechanism of toxicity. Furthermore, we will quantify biogenic elemental selenium uptake, depuration and biotransformation to proteinous forms (the species most relevant for trophic transfer). Thus we will be able to deliver an improved model of selenium food chain transfer in aquatic environments, the basis for appropriate selenium risk assessment. During the course of the proposed research, such questions as the following will be answered: - Is biogenic elemental selenium bioavailable and / or toxic to Daphnia magna? Which are the mechanisms underlying toxicity? - To which extent is biogenic selenium biotransformed to proteinous (highly bioaccumulative) species? Does biogenic elemental selenium represent a significant entrance port for selenium at base of aquatic food chain?
Das Projekt "SINCOS: Sinking Coasts - Geosphere, Ecosphere and Anthroposphere of the Holocene Southern Baltic Sea - Part 1.4: Changing sea levels and (semi)terrestrial landscape development in the Baltic Sea coastral area, with special attention to the role of the Darss Sill" wird/wurde ausgeführt durch: Ernst-Moritz-Arndt-Universität Greifswald, Institut für Botanik und Landschaftsökologie, Lehrstuhl für Landschaftsökologie und Ökosystemdynamik.The research unit SINCOS, established by the Deutsche Forschungsgemeinschaft, has been started in September 2002. The general target is the development of a model of the relation between geo-system, eco-system, climate and socio-economic system for sinking coasts of tideless seas to be developed as an example for the southern Baltic Sea since the Atlantikum. Geoscientists (geologists, geomorphologists, geodesists), biologists (palaeobotanists, palaezoologists), climate researchers and archaeologists will collaborate in order to investigate the cause and effect relation between driving forces (climatic and geological processes) and the response of the natural and social environment in the coastal areas of a transgressive sea. The reconstruction of the Litorina transgression west and east of the Darss sill structure plays the central role. Seven projects under the roof of SINCOS will deal with the acquisition and interpretation of proxy-data in order to reconstruct the history of the southwestern Baltic Sea since 8.000 calendar years BC. In the frame of two projects data will be integrated and models will be developed that mirror the processes of interrelation of different spheres to be investigated. Depending on the varying degree of quantification between measurable variables and qualitative observations models will differ between statistical data exploration and deterministic differential equations. A 4D GIS plays the central role in modelling and data integration. Results will be presented as time-dependent regionalizations of geo-, eco-, and socio-economical parameters. Simulations of future relative sea level change scenarios based on models developed are planned.